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authorMikhail Kshevetskiy <mikhail.kshevetskiy@gmail.com>2011-03-27 04:05:00 +0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-19 16:38:50 -0700
commit9db4e4381a8e881ff65a5d3400bfa471f84217e7 (patch)
tree5063e10432abf17472d9dd437f7451f553ef5be2
parent5680e94148a86e8c31fdc5cb0ea0d5c6810c05b0 (diff)
downloadlinux-9db4e4381a8e881ff65a5d3400bfa471f84217e7.tar.bz2
tty/n_gsm: fix bug in CRC calculation for gsm1 mode
Problem description: gsm_queue() calculate a CRC for arrived frames. As a last step of CRC calculation it call gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs); This work perfectly for the case of GSM0 mode as gsm->received_fcs contain the last piece of data required to generate final CRC. gsm->received_fcs is not used for GSM1 mode. Thus we put an additional byte to CRC calculation. As result we get a wrong CRC and reject incoming frame. Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@gmail.com> Acked-by: Alan Cox <alan@linux.intel.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/tty/n_gsm.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 47f8cdb207f1..74273e638c0d 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1658,8 +1658,12 @@ static void gsm_queue(struct gsm_mux *gsm)
if ((gsm->control & ~PF) == UI)
gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
- /* generate final CRC with received FCS */
- gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
+ if (gsm->encoding == 0){
+ /* WARNING: gsm->received_fcs is used for gsm->encoding = 0 only.
+ In this case it contain the last piece of data
+ required to generate final CRC */
+ gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
+ }
if (gsm->fcs != GOOD_FCS) {
gsm->bad_fcs++;
if (debug & 4)